The N-methyl pyrrolidone (called “NMP” for short), which is nitrogen heterocyclic compound, is one of the important industrial chemicals and widely applied in such fields as petroleum chemical industry, agricultural chemical, medicine and electronic material. The electronic grade N-methyl pyrrolidone can be used widely in the microelectron industry and in the semiconductor industry as the cleansing agent of precision instrument, circuit board photoresist, the solvent for liquid crystal (LCD) material production, the electrode accessory material of lithium battery, and so on. The purity and cleanliness of the N-methyl pyrrolidone have strongly influence on the yield of, the electricity property and the stability of the electronic products. In recent years, with the rapid development of the IT industry, the size of the integrated circuit is smaller and processing speed thereof is higher, and the demand to the purity of the electronic grade chemicals such as electronic grade N-methyl pyrrolidone is higher.
In the prior art, the N-methyl pyrrolidone is obtained through heating, pressurization and dehydration of N-methyl-4-hydroxyl butyrylamide which is produced by the reaction of the .gamma.-butyrolactone as material and methylamine, and this is the only industrial process for producing N-methyl pyrrolidone, and used by corporations such as American GAF, German BASF and the Japanese Mitsubishi and so on for mass production. In further purification process, because the difference between boiling points of the NMP and raw material .gamma.-butyrolactone is only 2° C., it is very difficult to divide the two reagents above by method of rectification. So the multilevel rectification method is commonly used for producing electronic grade reagents.
The U.S. Pat. No. 4,965,370 and the European patent EP346086A2 disclosed the same method for preparing highly purified NMP by adding alkaline metal or alkaline metal salt first into NMP (reacting system) to remove the metal ions, and then several rectifications to high purity NMP. Japanese patent JP06-279401A and JP08-109167A both use repeated distillation to obtain high purity NMP. However, it is difficult to produce NMP on the large scale through using the methods above because of their high cost and high energy consumption, difficult process control and high risk.